This invention relates to identification cards and the like provided with Fresnel holograms of pattern form, to a process for producing pattern-form Fresnel holograms, and to a method of verifying identification cards and the like provided with holograms.
At present, a great variety and great number of credit cards, cash cards, individual identification cards, transit tickets, commuters' passes, printed certificates, bank savings booklets, licenses, and the like are being used. In many instances, in order to prevent counterfeiting and other fraudulent acts, these articles of proof (hereinafter referred to collectively as ID article(s)), contain information of unique character for every ID article, which information cannot be directly read from the exterior and is recorded therein as a hidden or secret verification.
The most common method of recording such a secret verification is the magnetic recording method, which in may cases comprises providing a magnetic recording layer in a ribbon state at the upper part or a side part of an ID article and recording on this magnetic recording layer a secret number of four digits, for example, together with other information. The information thus recorded by this magnetic recording method is advantageous in that it is not visible from the outside and cannot be counterfeited by reproduction or duplication methods such as photographic and electrophotographic methods. However, since this method has been used over a long period, the magnetic recording and reproducing methods thereof are relatively well known and cannot be said to be positively proof against counterfeiting and leakage of information and counterfeiting and alteration of these ID articles are becoming a great social problem.
As a method capable of overcoming the inadequacy of this conventional magnetic recording method, the recording of necessary information by utilizing a diffraction grating or a certain kind of hologram has been proposed. This method, however, is also inadequate, being incapable of simultaneously satisfying the requirements of prevention of counterfeiting, facility of distinguishing the genuine or false nature of the ID article by visual inspection, and decorative nature or aesthetically pleasant appearance thereof.